The efficiency of improved oil recovery methods is evaluated using coreflooding systems. A coreflood system flows a fluid through a core sample at simulated reservoir conditions and measures flow parameters. Oil recovered from the coreflooding system can be present as a continuous oil phase, a water-in-oil emulsion containing a certain amount of water and an oil-in-water emulsion containing relatively small, or sometimes trace, amount of oil. The amount of oil from the coreflooding samples is analyzed through a variety of analytical methods to determine the success of oil recovery. These analytical methods include visual observation, infrared spectroscopy, near infra-red reflectance spectroscopy, nuclear magnetic resonance (NMR), and absorption spectroscopy. The cumulative produced oil volumes are determined with high levels of noise and uncertainty by real-time monitoring.
Visual observation involves a sample of the oil-water mixture placed in a graduated cylinder and allowed to separate into an oil phase and a water phase. The amount of oil is then determined based on the height of the oil phase in the graduated cylinder. Visual observation is inaccurate when the amount of oil is less than 0.1 mL. NIR spectroscopy requires a special instrument for the measurement and is sensitive to the changes in the texture of the samples. NMR also requires specialized and expensive equipment for measurement. An OCMA-300 series oil content analyzer can be used for measuring the oil content in emulsion samples. These methods all suffer from major drawbacks. They require expensive, complicated equipment and skilled operators, which adds to the expense of running a sample. The methods can analyze the emulsion samples, but not other samples with trace amounts of oil in water. These methods consume significant time to obtain results on a given sample. Fraction collection based oil quantification methods are very time consuming and laborious. Current practices involve multiple steps, with each step handled manually, thus making these steps error-prone. Fluid level-based methods of cumulative recovered oil monitoring give noisy data that impede evaluation of temporal aspects of improved oil recovery treatments.